The present invention relates to a protective guard for a hand-held rotary cut-off tool.
A hand-held rotary cut-off tool has an abrasive rotary cut-off disk driven by an electric or pneumatic motor, and is used to cut a workpiece. The cut-off tool typically has a protective guard that partially surrounds the cut-off disk.
FIG. 1 shows a prior art pneumatic hand-held rotary cut-off tool 10. The tool 10 has a housing 12 configured to be grasped by hand. The tool 10 also has an abrasive cut-off disk 14 attached to the end of an arbor 16, concentrically aligned along a rotational axis 18. A pneumatic motor 20 within a cavity 22 of the housing 12 rotates the arbor 16 and the cut-off disk 14 about the axis 18. The tool 10 also has a half-bell shaped protective guard 24. The guard 24 can swivel about the axis 18 as needed for adjustment but does not rotate with the disk 14.
FIG. 2 shows an exploded view of major components of the cut-off tool 10 of FIG. 1. The tool 10 has a nut 30 which serves to indirectly attach the guard 24 to the housing 12. The nut 30 has a non-threaded nut bore 32 extending along the axis 18 entirely through the nut 30. The nut 30 also has an external screw-thread 34 at one end, a torque structure 36, having two flats 38, at the other end, and a smooth nut shank portion 40 in-between. The nut shank portion 40 has a circumferentially-extending groove 42. A nut abutment surface 44 is located between the external screw-thread 34 and the nut shank portion 40.
The cut-off disk 14 is attached by a screw 46 to the arbor 16. The arbor 16 passes through the nut bore 32 and is connected to and rotated by an output shaft 48 of the motor 20. The nut 30 is screwed into the housing 12.
The guard 24 has a flat guard flange 50 with a mounting hole 52 that receives the nut shank portion 40. The guard flange 50 is held in place, on its axially-inner side, by a first flat washer 54, a wave washer 56 and the nut abutment surface 44. The guard flange 50 is held in place, on its axially-outer side, by a second flat washer 58 and a retaining ring 60 that snaps into the groove 42. The wave washer 56 is compressively engaged by and between the nut abutment surface 44 and the flat washer 54. Pressure from the wave washer 56 is transmitted through the flat washer 54 to the guard flange 50 and causes the guard 24 to be releasably restrained from swiveling about the nut shank portion 40.
FIG. 3 shows an exploded view of major components of a second prior art cut-off tool 62. The components and overall design of the second cut-off tool 62 are similar to those of the first cut-off tool 10. The second prior art cut-off tool 62 has a nut 64 which serves the same function as the nut 30 of the first cut-off tool 10. The nut 64 has a non-threaded nut bore 66. The nut 64 also has an external screw-thread 70 at one end, a smooth nut shank portion 72 at the other end, and a torque structure 74, having six flats 76, in-between. The nut shank portion 72 has a retaining ring groove 78. A nut abutment surface 80 is located between the torque structure 74 and the nut shank portion 72. The second cut-off tool 62 also has a guard 82 similar to the guard 24 of the first cut-off tool 10. A wave washer 84 is compressively engaged by and between the nut abutment surface 80 and a guard flange 86.
Some differences between the first and second prior art cut-off tools 10 and 62 are as follows. The second prior art tool 62 lacks the flat washers 54 and 58 of the first prior art tool 10. The shank portion 72, the torque structure 74 and the abutment surface 80 of the nut 64 of the second prior art tool 62 are disposed in a different sequence than the corresponding features (the shank portion 40, the torque structure 36, and the abutment surface 44) of the nut 30 of the first prior art tool 10.
In accordance with the invention, a rotary cut-off tool has a hand-held housing. The housing has an open end centered on an axis, and has a housing abutment surface facing axially outward of the open end. A motor within the housing has an output shaft extending along the axis. A guard has a guard flange with a mounting hole. An arbor is configured to extend axially from the shaft through the mounting hole. The tool further has a spring and a cut-off disk receivable on the arbor. The spring has an installed position compressively engaged by and between the housing abutment surface and the guard flange, such that the spring releasably restrains the guard from swiveling about the axis.
In a preferred embodiment of the invention, the housing further has an internal screw-thread centered on the axis, and the tool further has a tubular fitting. The fitting has a bore that receives the arbor. An external screw-thread on the fitting is engageable with the internal screw-thread in the housing. The fitting further has an axially facing abutment surface, and a shank portion between the fitting abutment surface and the external screw-thread. When installed, the spring is received over the shank portion of the fitting.